Christopher is $20$ years younger than Ishaan. Ishaan and Christopher first met two years ago. Fourteen years ago, Ishaan was $3$ times as old as Christopher. How old is Christopher now?
Answer: We can use the given information to write down two equations that describe the ages of Ishaan and Christopher. Let Ishaan's current age be $i$ and Christopher's current age be $c$. The information in the first sentence can be expressed in the following equation: ${i = c + 20}$ Fourteen years ago, Ishaan was $i - 14$ years old, and Christopher was $c - 14$ years old. The information in the third sentence can be expressed in the following equation: ${i - 14 = 3(c - 14)}$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $c$, it might be easiest to use our first equation for $i$ and substitute it into our second equation. Our first equation is: ${i = c + 20}$. Substituting this into our second equation, we get the equation: $ {(c + 20)}{-14 = 3(c - 14)} $ which combines the information about $c$ from both of our original equations. Simplifying both sides of this equation, we get: $c + 6 = 3 c - 42$. Solving for $c$, we get: $2 c = 48$. $c = 24$.